1. Field of the Invention
This invention relates to a current sensing relay and, more specifically, to a plural pole relay for magnetically opening a normally closed switch of a circuit upon sensing of a predetermined electrical current.
2. Brief Description of the Prior Art
In accordance with the prior art, filament windings of fluorescent lamps and the like remain in an energized state after lighting of the lamp since there is no provision for cutting off the filament current after commencement of lamp operation. This condition results in waste of energy as well as production of possibly unwanted heat which also must be dissipated in some manner. The prior art has attempted to alleviate this problem in several ways, such as by the use of timers in the filament circuits to cut off current to the filaments after a predetermined period of time. Other solutions to the problem are shown in Latassa (U.S. Pat. No. 4,009,412) wherein there is provided a secondary winding to supply lamp current and a tertiary winding to supply heater current wherein a magnetic switch is provided which senses current through the secondary winding and opens the heater current circuit in response thereto. Other prior art of this type is shown in Feinberg (U.S. Pat. No. 4,568,860), Citino (U.S. Pat. No. 4,661,745), Fuller (U.S. Pat. No. 4,559,478), Regan (U.S. Pat. No. 4,339,690), Morton (U.S. Pat. No. 4,082,981) and Powell (U.S. Pat. No. 3,866,087). These prior art solutions have been subject to one or more of several problems, these including cost, the use of normally open switches wherein the switch must close to ignite the lamps initially and switch failure therefor results in fixture lighting failure. It is therefore apparent that a mechanism is required which can provide the above described result in a more economic and failure-safe manner.